-- Prosody IM v0.4

-- Copyright (C) 2008-2009 Matthew Wild

-- Copyright (C) 2008-2009 Waqas Hussain

-- 

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

local hosts = hosts;

local sessions = sessions;

local core_process_stanza = function(a, b) core_process_stanza(a, b); end

local add_task = require "util.timer".add_task;

local socket = require "socket";

local format = string.format;

local t_insert, t_sort = table.insert, table.sort;

local get_traceback = debug.traceback;

local tostring, pairs, ipairs, getmetatable, newproxy, error, tonumber

    = tostring, pairs, ipairs, getmetatable, newproxy, error, tonumber;

local idna_to_ascii = require "util.encodings".idna.to_ascii;

local connlisteners_get = require "net.connlisteners".get;

local wrapclient = require "net.server".wrapclient;

local modulemanager = require "core.modulemanager";

local st = require "stanza";

local stanza = st.stanza;

local nameprep = require "util.encodings".stringprep.nameprep;

local uuid_gen = require "util.uuid".generate;

local logger_init = require "util.logger".init;

local log = logger_init("s2smanager");

local sha256_hash = require "util.hashes".sha256;

local dialback_secret = uuid_gen();

local adns = require "net.adns";

local dns_timeout = config.get("*", "core", "dns_timeout") or 60;

incoming_s2s = {};

local incoming_s2s = incoming_s2s;

module "s2smanager"

local function compare_srv_priorities(a,b) return a.priority < b.priority or a.weight < b.weight; end

local function bounce_sendq(session)

	local sendq = session.sendq;

	if sendq then

		session.log("info", "sending error replies for "..#sendq.." queued stanzas because of failed outgoing connection to "..tostring(session.to_host));

		local dummy = {

			type = "s2sin";

			send = function(s)

				(session.log or log)("error", "Replying to to an s2s error reply, please report this! Traceback: %s", get_traceback());

			end;

			dummy = true;

		};

		for i, data in ipairs(sendq) do

			local reply = data[2];

			local xmlns = reply.attr.xmlns;

			if not xmlns or xmlns == "jabber:client" or xmlns == "jabber:server" then

				reply.attr.type = "error";

				reply:tag("error", {type = "cancel"})

					:tag("remote-server-not-found", {xmlns = "urn:ietf:params:xml:ns:xmpp-stanzas"}):up();

				core_process_stanza(dummy, reply);

			end

			sendq[i] = nil;

		end

		session.sendq = nil;

	end

end

function send_to_host(from_host, to_host, data)

	local host = hosts[from_host].s2sout[to_host];

	if host then

		-- We have a connection to this host already

		if host.type == "s2sout_unauthed" and data.name ~= "db:verify" and ((not data.xmlns) or data.xmlns == "jabber:client" or data.xmlns == "jabber:server") then

			(host.log or log)("debug", "trying to send over unauthed s2sout to "..to_host);

			if not host.notopen and not host.dialback_key and host.sends2s then

				host.log("debug", "dialback had not been initiated");

				initiate_dialback(host);

			end

			-- Queue stanza until we are able to send it

			if host.sendq then t_insert(host.sendq, {tostring(data), st.reply(data)});

			else host.sendq = { {tostring(data), st.reply(data)} }; end

			host.log("debug", "stanza [%s] queued ", data.name);

		elseif host.type == "local" or host.type == "component" then

			log("error", "Trying to send a stanza to ourselves??")

			log("error", "Traceback: %s", get_traceback());

			log("error", "Stanza: %s", tostring(data));

		else

			(host.log or log)("debug", "going to send stanza to "..to_host.." from "..from_host);

			-- FIXME

			if host.from_host ~= from_host then

				log("error", "WARNING! This might, possibly, be a bug, but it might not...");

				log("error", "We are going to send from %s instead of %s", tostring(host.from_host), tostring(from_host));

			end

			host.sends2s(data);

			host.log("debug", "stanza sent over "..host.type);

		end

	else

		log("debug", "opening a new outgoing connection for this stanza");

		local host_session = new_outgoing(from_host, to_host);

		-- Store in buffer

		host_session.sendq = { {tostring(data), st.reply(data)} };

		log("debug", "stanza [%s] queued until connection complete", tostring(data.name));

		if (not host_session.connecting) and (not host_session.conn) then

			log("warn", "Connection to %s failed already, destroying session...", to_host);

			destroy_session(host_session);

		end

	end

end

local open_sessions = 0;

function new_incoming(conn)

	local session = { conn = conn, type = "s2sin_unauthed", direction = "incoming", hosts = {} };

	if true then

		session.trace = newproxy(true);

		getmetatable(session.trace).__gc = function () open_sessions = open_sessions - 1; end;

	end

	open_sessions = open_sessions + 1;

	local w, log = conn.write, logger_init("s2sin"..tostring(conn):match("[a-f0-9]+$"));

	session.sends2s = function (t) log("debug", "sending: %s", tostring(t)); w(tostring(t)); end

	incoming_s2s[session] = true;

	return session;

end

function new_outgoing(from_host, to_host)

		local host_session = { to_host = to_host, from_host = from_host, notopen = true, type = "s2sout_unauthed", direction = "outgoing" };

		hosts[from_host].s2sout[to_host] = host_session;

		local log;

		do

			local conn_name = "s2sout"..tostring(host_session):match("[a-f0-9]*$");

			log = logger_init(conn_name);

			host_session.log = log;

		end

		attempt_connection(host_session);

		if not host_session.sends2s then		

			-- A sends2s which buffers data (until the stream is opened)

			-- note that data in this buffer will be sent before the stream is authed

			-- and will not be ack'd in any way, successful or otherwise

			local buffer;

			function host_session.sends2s(data)

				if not buffer then

					buffer = {};

					host_session.send_buffer = buffer;

				end

				log("debug", "Buffering data on unconnected s2sout to %s", to_host);

				buffer[#buffer+1] = data;

				log("debug", "Buffered item %d: %s", #buffer, tostring(data));

			end

		end

		return host_session;

end

function attempt_connection(host_session, err)

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local connect_host, connect_port = idna_to_ascii(to_host), 5269;

	if not err then -- This is our first attempt

		log("debug", "First attempt to connect to %s, starting with SRV lookup...", to_host);

		host_session.connecting = true;

		local answer, handle;

		handle = adns.lookup(function (answer)

			handle = nil;

			host_session.connecting = nil;

			if answer then

				log("debug", to_host.." has SRV records, handling...");

				local srv_hosts = {};

				host_session.srv_hosts = srv_hosts;

				for _, record in ipairs(answer) do

					t_insert(srv_hosts, record.srv);

				end

				t_sort(srv_hosts, compare_srv_priorities);

				local srv_choice = srv_hosts[1];

				host_session.srv_choice = 1;

				if srv_choice then

					connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

					log("debug", "Best record found, will connect to %s:%d", connect_host, connect_port);

				end

			else

				log("debug", to_host.." has no SRV records, falling back to A");

			end

			-- Try with SRV, or just the plain hostname if no SRV

			return try_connect(host_session, connect_host, connect_port);

		end, "_xmpp-server._tcp."..connect_host..".", "SRV");

		-- Set handler for DNS timeout

		add_task(dns_timeout, function ()

			if handle then

				adns.cancel(handle, true);

			end

		end);

		log("debug", "DNS lookup for %s sent, waiting for response before we can connect", to_host);

		return true; -- Attempt in progress

	elseif host_session.srv_hosts and #host_session.srv_hosts > host_session.srv_choice then -- Not our first attempt, and we also have SRV

		host_session.srv_choice = host_session.srv_choice + 1;

		local srv_choice = host_session.srv_hosts[host_session.srv_choice];

		connect_host, connect_port = srv_choice.target or to_host, srv_choice.port or connect_port;

		host_session.log("info", "Connection failed (%s). Attempt #%d: This time to %s:%d", tostring(err), host_session.srv_choice, connect_host, connect_port);

	else

		host_session.log("info", "Out of connection options, can't connect to %s", tostring(host_session.to_host));

		-- We're out of options

		return false;

	end

	if not (connect_host and connect_port) then

		-- Likely we couldn't resolve DNS

		log("warn", "Hmm, we're without a host (%s) and port (%s) to connect to for %s, giving up :(", tostring(connect_host), tostring(connect_port), tostring(to_host));

		return false;

	end

	return try_connect(host_session, connect_host, connect_port);

end

function try_connect(host_session, connect_host, connect_port)

	host_session.log("info", "Beginning new connection attempt to %s (%s:%d)", host_session.to_host, connect_host, connect_port);

	-- Ok, we're going to try to connect

	local from_host, to_host = host_session.from_host, host_session.to_host;

	local conn, handler = socket.tcp()

	conn:settimeout(0);

	local success, err = conn:connect(connect_host, connect_port);

	if not success and err ~= "timeout" then

		return false;

	end

	local cl = connlisteners_get("xmppserver");

	conn = wrapclient(conn, connect_host, connect_port, cl, cl.default_mode or 1, hosts[from_host].ssl_ctx, false );

	host_session.conn = conn;

	-- Register this outgoing connection so that xmppserver_listener knows about it

	-- otherwise it will assume it is a new incoming connection

	cl.register_outgoing(conn, host_session);

	local w = conn.write;

	host_session.sends2s = function (t) log("debug", "sending: %s", tostring(t)); w(tostring(t)); end

	conn.write(format([[<stream:stream xmlns='jabber:server' xmlns:db='jabber:server:dialback' xmlns:stream='http://etherx.jabber.org/streams' from='%s' to='%s' version='1.0' xml:lang='en'>]], from_host, to_host));

	log("debug", "Connection attempt in progress...");

	return true;

end

function streamopened(session, attr)

	local send = session.sends2s;

	-- TODO: #29: SASL/TLS on s2s streams

	session.version = 0; --tonumber(attr.version) or 0;

	if session.version >= 1.0 and not (attr.to and attr.from) then

		log("warn", (session.to_host or "(unknown)").." failed to specify 'to' or 'from' hostname as per RFC");

	end

	if session.direction == "incoming" then

		-- Send a reply stream header

		session.to_host = attr.to and nameprep(attr.to);

		session.from_host = attr.from and nameprep(attr.from);

		session.streamid = uuid_gen();

		(session.log or log)("debug", "incoming s2s received <stream:stream>");

		send("<?xml version='1.0'?>");

		send(stanza("stream:stream", { xmlns='jabber:server', ["xmlns:db"]='jabber:server:dialback', 

				["xmlns:stream"]='http://etherx.jabber.org/streams', id=session.streamid, from=session.to_host }):top_tag());

		if session.to_host and not hosts[session.to_host] then

			-- Attempting to connect to a host we don't serve

			session:close({ condition = "host-unknown"; text = "This host does not serve "..session.to_host });

			return;

		end

		if session.version >= 1.0 then

			send(st.stanza("stream:features")

					:tag("dialback", { xmlns='urn:xmpp:features:dialback' }):tag("optional"):up():up());

		end

	elseif session.direction == "outgoing" then

		-- If we are just using the connection for verifying dialback keys, we won't try and auth it

		if not attr.id then error("stream response did not give us a streamid!!!"); end

		session.streamid = attr.id;

		-- Send unauthed buffer

		-- (stanzas which are fine to send before dialback)

		-- Note that this is *not* the stanza queue (which 

		-- we can only send if auth succeeds) :)

		local send_buffer = session.send_buffer;

		if send_buffer and #send_buffer > 0 then

			log("debug", "Sending s2s send_buffer now...");

			for i, data in ipairs(send_buffer) do

				session.sends2s(tostring(data));

				send_buffer[i] = nil;

			end

		end

		session.send_buffer = nil;

		if not session.dialback_verifying then

			initiate_dialback(session);

		else

			mark_connected(session);

		end

	end

	session.notopen = nil;

end

function streamclosed(session)

	(session.log or log)("debug", "</stream:stream>");

	if session.sends2s then

		session.sends2s("</stream:stream>");

	end

	session.notopen = true;

end

function initiate_dialback(session)

	-- generate dialback key

	session.dialback_key = generate_dialback(session.streamid, session.to_host, session.from_host);

	session.sends2s(format("<db:result from='%s' to='%s'>%s</db:result>", session.from_host, session.to_host, session.dialback_key));

	session.log("info", "sent dialback key on outgoing s2s stream");

end

function generate_dialback(id, to, from)

	return sha256_hash(id..to..from..dialback_secret, true);

end

function verify_dialback(id, to, from, key)

	return key == generate_dialback(id, to, from);

end

function make_authenticated(session, host)

	if session.type == "s2sout_unauthed" then

		session.type = "s2sout";

	elseif session.type == "s2sin_unauthed" then

		session.type = "s2sin";

		if host then

			session.hosts[host].authed = true;

		end

	elseif session.type == "s2sin" and host then

		session.hosts[host].authed = true;

	else

		return false;

	end

	session.log("debug", "connection %s->%s is now authenticated", session.from_host or "(unknown)", session.to_host or "(unknown)");

	mark_connected(session);

	return true;